The present invention relates to a method for inspecting a thermal assist type magnetic head which inspects thermal assist type magnetic head, and an apparatus for inspecting a thermal assist type magnetic head, and in particular to, in the techniques such as optical microscopes, a method and apparatus for inspecting thermal assist type magnetic head which is capable of inspecting the state of generation of near-field light generated by a thermal assist type magnetic head which cannot be inspected.
As apparatuses which non-destructively inspect magnetic heads, a method using an optical microscope, a method using a scanning electron microscope (SEM), a method using an atomic force microscope (AFM), and a method using a magnetic force microscope (MFM), among others, have been employed.
Each of the methods mentioned above has its merits and demerits. Since a magnetic field generated by a magnetic head for writing on a hard disk can be non-destructively inspected, the method using a magnetic force microscope (MFM) is advantageous over the methods using observation means by other systems.
Using this magnetic force microscope (MFM), measuring the effective track width of a write track in a state of a row bar in which a plurality of magnetic head elements are placed side by side before the magnetic head elements formed on a wafer are separated individually, for example, is described in Japanese Unexamined Patent Publication No. 2010-175534 (patent document 1). That is, patent document 1 describes generating a magnetic field by applying a current to a magnetic head circuit pattern of a sample, i.e., a row bar, and a magnetic probe attached to a cantilever is approached to this magnetic field generating by performing two-dimensional measurement of the magnetic field generated by the sample by two-dimensionally scanning the cantilever to detect the displacement magnitude of the probe of the cantilever.
Moreover, Japanese Unexamined Patent Publication No. 2009-230845 (patent documents 2) describes a conventional magnetic head inspection as follows: in a magnetic head inspection, a record signal (signal for magnetization) is inputted into a thin film magnetic head in a magnetic head row bar state from a bonding pad. The situation of the magnetic field generated from the recording head (element) contained in the thin film magnetic head is observed while the thin film magnetic head is scanned and moved in the position corresponding to the floating height of the magnetic head. The situation of this magnetic field is directly observed under a magnetic force microscope (MFM), a scanning hall probe microscope (SHPM), or a scanning magneto-resistive effect microscope (SMRM). This allows measurement of not physical forms but the magnetic field configuration generated, and non-destructive inspection of magnetic effective track widths. Japanese Unexamined Patent Publication No. 2009-230845 (patent documents 2) describes achieving measurement of the effective track widths in the state of a row bar by using a magnetic force microscope, which has been only possible in the state of HGA or pseudo-HGA using a spin stand.
In contrast, as new techniques for next-generation hard disks for which dramatically higher capacities are demanded, magnetic recording methods by thermal assist have been drawing attention and are increasingly developed in many companies. Increasing densities and capacities of hard disks requires reduction in their track widths, which are said to have almost reached their limits in magnetic heads of conventional systems, but employing a magnetic head of the thermal assist method using near-field light as a heat source allows realization of a track width of about 20 nm.
In this thermal assist magnetic recording head, near-field light is generated using a conductive structure having such a cross sectional shape that the width in the direction perpendicular to the polarization direction of incident light propagating through a waveguide gradually decreases towards the vertex where the near-field light is generated, and, its width decreases gradually or stepwise towards the vertex where the near-field light is generated in the direction of travel of the incident light. A configuration in which the waveguide is disposed next to a structure having conductivity, and near-field light is generated via surface plasmon generated on the side face the structure having conductivity is described in Japanese Unexamined Patent Publication No. 2011-146097 (patent document 3).
However, the effective intensity distribution and size of the near-field light which serve as significant factors for this track width cannot be measured from surface shapes observed with optical microscopes and SEMs. Therefore, inspection methods are important issued which are left unsolved.
In contrast, as a technique for detecting this near-field light, patent document 4 discloses “Near-field optical microscope (also referred to as SNOM: Scanning Near-field Optical Microscopy, NSOM: Near-field Scanning Optical Microscopy, NOM: Near-field Optical Microscopy)”, which can detect near-field light and determine its configuration by approaching a scanning type probe to the near-field light, and scattering the near-field light.